MICHAEL FLYNN WAS an impending train wreck you could spot from miles away. His firing — after the revelation that he had discussed then-President Obama’s election-meddling sanctions against Russia with Russian Ambassador Sergey Kislyak, on the very day they were announced, and subsequently lied about it — removes one conspiracist, paranoid, scheming figure from the core of Donald Trump’s national security operation.

Flynn’s departure won’t dissipate the shadow l’affaire Flynn casts over this chaotic, incompetent White House. It might, however, be a leverage point for Secretary of Defense Jim Mattis and Secretary of State Rex Tillerson to assert more control over the national security apparatus. That means privately demanding that Trump rescind his ill-considered appointment of Steve Bannon, another pugnacious, paranoid schemer, to a seat on the National Security Council.

That would at least shore up the national security/foreign policy aspect of the administration. It won’t, of course, address Team Trump’s myriad other dysfunctions. Not while Bannon and Steve Miller, his 31-year-old Iago-esque understudy and fellow mastermind of the travel-ban debacle, remain in Trump’s inner circle.

Nor will Flynn’s departure end the questions about this administration’s disquieting relationship with Russia. Flynn’s deception was so pronounced that former acting attorney general Sally Yates decided she should notify the new administration that its national security adviser had lied and might be susceptible to Russian blackmail.

And yet the administration didn’t take any action until The Washington Post broke that story. Indeed, when reporters asked Trump on Friday about “reports” of Flynn’s pre-inauguration sanctions discussions with Kislyak, Trump dissembled, saying: “I don’t know about it. I haven’t seen it. What report is that?” Told what the Post was reporting, he replied: “I haven’t seen that. I’ll look into it.”

But as White House press secretary Sean Spicer said Tuesday, Trump had known about Flynn’s duplicity since the Department of Justice notified the White House on Jan. 26. Spicer claimed that Trump hadn’t instructed Flynn to have those sanction discussions and that he wasn’t aware that the matter had come up in Flynn’s conversation with the Russian ambassador, but honestly, given the truth-challenged nature of this administration, who can take either assertion at face value?

Suspicions abound that Trump himself could have some compromising liabilities vis-a-vis Russia — perhaps financial entanglements, perhaps something more lurid. If Trump released his tax returns, light might be shed on that matter, but he has, of course, reneged on that promise.

We need an investigation, with witnesses under oath, to get to the bottom of all this.

So far, the Republican-led House, which was ready to investigate Barack Obama or Hillary Clinton at the drop of a hat, has shown little interest. Jason Chaffetz, chairman of the House Oversight Committee, said Tuesday that this “situation has taken care of itself” (!) and, like a purblind political ground hog, retreated into his burrow for a long winter’s nap. House Intelligence Committee Chairman Devin Nunes has preemptively declared investigative surrender, maintaining that any conversations between Flynn and Trump would be protected by executive privilege. Neither man, it’s safe to say, will receive a spinal injection from Speaker Paul Ryan, the incredible shrinking speaker.

But despite a reluctant leader of their own, the Senate has started to rumble with discontent. Republican Senators Lindsey Graham, Roy Blunt, Bob Corker, and others have spoken up to ask important questions or push for real oversight.

The more lawmakers hear from constituents, be it at town meetings or by phone, e-mail, or letter, that they want and expect a thorough probe, the more likely it is that that will happen. These strange times call for an active, engaged, insistent citizenry.